Apparatus for making a flexible link belt

ABSTRACT

A flexible link belt is made by injection molding link portions into and through a flexible carrier webbing, whereby the link portions are also bonded to each other through holes in the webbing. The injection mold used for making the links has two mold sections each with a cavity portion corresponding to the respective link portion. The carrier webbing is held in place between the two mold sections. An injection nozzle reaches into one mold portion and a movable core reaches into the other mold portion preferably in such a position that the injection nozzle and the movable core face each other across the flexible webbing. The core distributes the injected plastics material into both mold portions and so that the plastics material must move primarily through the holes or interstices in the webbing.

FIELD OF THE INVENTION

The invention relates to a flexible link belt, to a method for makingsuch link belts, and to an apparatus for performing the manufacturingmethod of the present link belt.

DESCRIPTION OF THE PRIOR ART

Flexible link belts and tapes are known, for example, in the form ofgear belts having different configurations for different purposes. Priorart gear belts are made as multi-layer structures forming endless loops.It is difficult to construct such multi-layer link belts. Hence, theirmanufacture is involved and expensive.

OBJECTS OF THE INVENTION

In view of the foregoing it is the aim of the invention to achieve thefollowing objects singly or in combination:

to provide a link belt which is modifiable for many different purposesin an easy manner;

to provide a link belt or tape to which the links are rigidly andpermanently secured without the need for punching holes or the likethrough the carrier tape or belt;

to use as a carrier tape or belt a webbing in which the naturallyoccurring interstices or holes between the weft and warp threads aresufficient for intimately bonding the links into and through thewebbing;

to provide strips or tapes on which the links are formed as snapfasteners, whereby the tapes then may be used for many differentpurposes;

to provide a method for manufacturing such link belts by making eitherone belt at a time or a plurality of belts simultaneously; and

to provide an injection mold suitable for performing the present method.

SUMMARY OF THE INVENTION

According to the invention the present link belts are manufactured bythe following steps. A carrier strip or webbing is used which hasnaturally occurring interstices or holes therein as a result of theweaving. The interstices remaining even after a tight weaving aresuitable for the present purpose. A synthetic material is injected underpressure into mold cavity portions so that the links are formed alongthe flexible carrier webbing with a spacing between neighboring links.Each link is formed with two link portions, one on one side of thewebbing and the other link portion on the other side of the webbing. Thelink portions are bonded to each other through the webbing, whereby thewebbing may even form a reinforcement of the links as in a fibercomposite material.

The injection mold according to the invention is characterized in that afirst mold section having at least one synthetic material injectionnozzle is arranged on one side of the flexible carrier webbing. Thefirst mold section is provided with a mold cavity portion correspondingto the shape of the desired link portion. The flexible carrier webbingcloses the mold portion except for the interstices or holes naturallyoccurring in the webbing. Preferably, the injection nozzle is locatedcentrally in its respective mold cavity portion. The opening of theinjection nozzle either directly contacts the webbing or almost contactsthe webbing. The present injection mold is further characterized by asecond mold section also having a mold cavity portion for cooperationwith the first mentioned mold cavity portion in the first mold sectionacross the webbing. Thus, the webbing is clamped in place between thetwo mold sections. A movable mold core is arranged to pass through thesecond mold cavity portion for cooperation with the injection nozzleacross the carrier webbing. The core either directly contacts thewebbing or almost contacts the webbing. Further, the core is movableperpendicularly to the longitudinal extension of the carrier webbing.

The link belt according to the invention is characterized in that itcomprises a plurality of synthetic material links spaced from oneanother along the belt. Each link comprises two link portions, one oneach side of the belt and intimately and permanently bonded to eachother through the naturally occurring interstices in the belt orwebbing.

The teaching of the invention assures a permanent, non-releasableconnection between the two link portions and the flexible belt orwebbing without the need for first weakening the belt or webbing bymaking holes at the connecting points. By avoiding the making ofseparate holes and instead using the naturally occurring interstices orholes in a webbing, for example of glass fibers, the invention avoidsany fraying of the webbing at the locations of the links. Further,manufacture is simplified by the avoidance of punching holes through thewebbing.

By arranging the injection nozzle and the movable core according to theinvention so that both face each other across the webbing, therebyeither directly contacting the webbing or almost contacting the webbing,the core will support the webbing so that the webbing will not bulge inresponse to the relatively high injection pressure under which theliquid synthetic material impacts on the webbing.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be clearly understood, it will now bedescribed, by way of example, with reference to the accompanyingdrawings, wherein:

FIG. 1 is a sectional view through an injection mold according to theinvention for producing members of a snap button permanently secured toa flexible carrier webbing, and showing a first phase in the injectionmolding process;

FIG. 2 is a view similar to that of FIG. 1, but showing a second phasein the injection molding process;

FIG. 3 is a sectional view similar to that of FIGS. 1 and 2, but showinga third phase in the injection molding process;

FIG. 4 is a view similar to that of FIGS. 1, 2, and 3, but illustratinga mold for the production of link belts in which the links are teeth toform a gear belt;

FIG. 5 is a plan view onto a portion of a link belt according to theinvention provided with gear teeth having a circular top planconfiguration;

FIG. 6 is a side view of FIG. 5 showing the configuration of the gearteeth;

FIG. 7 shows a gear belt according to the invention, cooperating with apulley constructed for cooperation with a gear belt according to theinvention;

FIG. 8 shows a gear belt according to the invention in which the linksforming the gear teeth face away from the gear belt in alternateopposite directions so that the gear belt may run across two or morepulleys rotating in opposite directions; and

FIGS. 9a and 9b show two differently shaped links or rather teeth onrespective gear belts.

DETAILED DESCRIPTION OF PREFERRED EXAMPLE EMBODIMENTS AND OF THE BESTMODE OF THE INVENTION

The injection mold according to the invention shown in FIGS. 1 2, and 3is used for manufacturing snap button components having a first orcounter portion 22 and a second or male portion 20. The female snapbutton components are manufactured in the same manner and hence therespective injection mold and the manufacturing steps are not described.Each male portion has a conically back tapering outer wall 3 which willsnap into a respective recess of a female snap button component.

The injection mold according to the invention comprises a first uppermold section 4 and a second lower mold section 8. The upper mold section4 comprises supply ducts 5' for supplying an injection molding material5, such as synthetic plastics material to an injection nozzle 6. Theinjection nozzle 6 is located centrally in a first cavity portion 7which cooperates with a second cavity portion 10 in the second moldsection 8 to form a complete mold cavity through which the flexiblecarrier belt or webbing 1 extends in a manner separating the cavityportions 7 and 10 from each other. The injection nozzle 6 eitherdirectly contacts the webbing 1 or it is closely spaced from thewebbing 1. The downwardly facing surface of the upper mold section 4 andthe upwardly facing surface of the lower mold section 8 form means forholding the flexible carrier webbing 1 in place. An improved holding ofthe webbing 1 may be achieved by grooves 18 in one of the mold sectionsand ridges 16 cooperating with the grooves in the other mold section.

The cavity portion or portions 10 in the lower mold section 8 determinethe configuration of the functional portion 20 of the snap button. Thecavity portion 10 has a smaller diameter close to the webbing 1 than atits bottom to provide for the desired conical shape of the male portion20 of the snap button for assuring the desired press fit when the maleportion 20 is inserted into a respective female recess of a snap buttoncomponent. The cavity portion 7 forms a flat ring disk shape and thering disk is arranged coaxially relative to the lower cavity portion 10with regard to a central vertical axis not shown. The press fit providedby the ridge 16 and by the groove 18 makes sure that a sharp boundary isprovided along the circumferential edge of the ring disk 7. An axiallymovable core 12 mounted for an axial sliding movement in an ejector 14passes with its upper, preferably conical end centrally into the moldcavity portion 10, preferably directly opposite the nozzle 6 so that thenozzle and the upwardly facing surface of the conical end of the core 12face each other across the webbing 1. Preferably, the downwardly facingedge of the injection nozzle 6 and the upwardly facing surface of thecore 12 directly contact the webbing 1 or are only slightly spaced fromthe webbing for preventing the mentioned bulging of the webbing 1 whenthe injection molding pressure is effective. The ejector 14 surroundsthe core 12 in a movable manner. The upper end of the ejector 14 islocated to form part of the cavity portion 10. Additionally, the ejector14 is axially movable relative to the lower mold section 8 for pushingthe finished male snap button portion 20 out of the cavity 10 after thecore 12 has been withdrawn to easily remove the strip of the webbing 1with its snap button components out of the lower mold section 8.

The flexible carrier webbing 1 may be woven tightly and comprises theconventional warp and weft threads. The interstices remaining even aftera tight weaving form sufficient holes so that the synthetic plasticsmaterial injected under pressure into the webbing 1 will pass throughthe webbing 1 for filling the ring cavity portion 7 and the furthercavity portion 10, whereby the upper end of the core 12 sufficientlysupports the webbing 1 so that the webbing 1 will be prevented frombulging downwardly in response to the injection molding pressure whichcauses the liquid, hot synthetic molding material to pass through theinterstices or holes in the webbing for completely filling the cavityportions 7 and 10.

During the first phase of the injection molding the hot liquid syntheticmaterial under pressure will first enter into the interstices as shownin FIG. 1. Due to the counter holding by the core 12 the material mustyield in a horizontal lateral direction, whereby it will pass throughthe interstices in the carrier webbing 1 and out again into the cavityportions 7 and 10. First, the cavity 7 will be filled and thereafter thecavity 10 will be filled in a second phase of the injection moldingoperation as shown in FIG. 2.

At the end of the second phase both cavities are completely filled asshown in FIG. 3. Thereafter, the two snap button portions 20 and 22 areintimately bonded to each other through the webbing 1 which may evenform a reinforcement of the snap button component. After curing, themold sections 4 and 8 are separated from one another, the core 12 iswithdrawn and the ejector 14 is moved upwardly to eject the snap buttoncomponent 20, 22 from the cavity 10 together with the webbing 1. Thesynthetic material is sufficiently elastic so that it will assume theshape it had within the cavity 10 after it has passed out of the cavity10 through the narrowest cross-section at the top of the cavity 10.

Where a single injection mold is used as just described, the carrierwebbing 1 may be automatically stepped in synchronism with the operationof the mold sections 4 and 8 so that the snap button components areuniformly spaced from one another along a strip, tape, or belt of thewebbing 1.

However, production efficiency may be substantially increased if severalinjection molds are arranged in a row so that a plurality of webbings 1may be passed in parallel through such an injection mold. A wide stripof webbing may also be passed through such a mold and the webbing maythen be cut between rows of links so formed in the wide webbing. In anyevent, the number of snap button components arranged in a row or rows onthe carrier webbing may be selected as desired. Further, a plurality ofinjection molds may be arranged in rows and columns so as to form, forexample six, snap button components in a row with four or more rows ofsuch components being arranged in side-by-side relationship

Snap button tapes or belts as just described are useful for manypurposes. A preferred use is made in connection with the hanging ofcurtains. A strip with one type of said fastener components is securedto the curtains, for example by stiching, the opposite type of fastenercomponents is secured, for example, to the curtain rod, for example inthe form of so-called gliders capable of riding back and forth along arail forming part of the curtain rod. The flexibility of the webbing 1permits the formation of the customary curtain folds without interferingwith such formation. Since there are no metal parts in the snap buttonstrips according to the invention it is possible to wash the stripsalong with the curtains without any danger of damaging or destroying thewashing machine, especially its drum, and without any danger ofdestroying any surface coating that may have been applied to the snapbutton components.

FIG. 4 shows an injection mold for manufacturing and securing of gearteeth to a flexible tape or belt. The injection mold of FIG. 4 has thesame construction as that shown in FIGS. 1 to 3. Merely the cavity 24has the shape of the desired tooth rather than that of a snap button.

Here again, the webbing 1 may be of the tightly woven type having warpand weft threads. In spite of such tight weaving there remainsinterstices or holes between the threads in the webbing which are hardlyvisible by the bare eye. Yet, it has been found that these smallinterstices or holes are sufficient for the liquid, hot syntheticmolding material to pass through the webbing 1 under the high injectionmolding pressure. The webbing 1 thus does not require any separateperforation step for making holes in those places where the teeth are tobe attached. The counter portion for the tooth 23 is the same as thatfor the snap button and therefore is also referred to by referencenumber 22. The counter portion 22 is permanently bonded through thewebbing 1 with the tooth 23 when the injection molding operation iscompleted, and the plastics material has been cured.

The core 12 is then withdrawn and the tooth 23 pushed out of the cavity24 with the aid of the ejector 14 after the mold sections 4 and 8 havebeen separated. Depending on the shape of the teeth 23, it may not benecessary to provide an ejector 14 or it may be possible to accomplishthe ejection by bursts of air under pressure. The core 12 has flatslightly slanted side walls 28 which are easily withdrawn either duringor after the injection molding as will be described below with referenceto FIGS. 9a and 9b.

Synthetic plastics material suitable for making snap button componentsas well as teeth 23 and counter portions 22 comprise thermoplasticmaterials such as polyamide (Nylon 6) acetyl resin (copolymer orhomopolymers), polyethylene, and polyester materials.

The warp and weft threads of the webbing 1 are also made of the same ora similar compatible thermoplastic, heat weldable synthetic materialsuch as polyester, polyamide, polypropylene, or polyethylene. Thus, thebonding between the counter portion 22 and the snap button portion 20 orwith the teeth 23 and with the material of the webbing is very strongand permanent. In order for the counter portion 22 to assume the outlineor shape or curvature of a pinion, it is sufficiently thin to have therequired flexability.

The injection molding pressure applied, according to the invention ispreferably within the range of 300 to 800 bar and will depend on thetype material used. For example, when polyester is used the injectionmolding pressure is near to the lower end of the range, while it is nearto the upper range for acetyl resins.

An efficient cost effective manufacturing is accomplished when for eachinjection molding operation a plurality of links are formed, for examplefour to six in a row with predetermined spacings between neighboringlinks along the belt 1. The teeth 23 and the counter portions 22 arespaced in accordance with the cavities distributed around thecircumference of a pinion as shown for example in FIG. 7.

Further, the injection molding tool is constructed to comprise severalnozzles arranged in a pattern so that a plurality of webbings or a widewebbing may be passed through the tool. Thus, for example, a pluralityof injection nozzles 6 may form the respective plurality of links in awebbing 1 at the same time. Upon completion of one injection moldingstep, the webbing strips or a wide webbing strip will be advanced forperforming further injection molding steps in which a plurality of linksare formed simultaneously. The feed advance is such that the on-centerspacing of all links formed will be uniform.

FIGS. 5 and 6 illustrate a gear belt 1' carrying a plurality of teeth 23intimately bonded to the counter elements 22 through the webbing formingthe belt 1'. The teeth 23 are round in their cross-section and have anevolvent configuration. Compared to conventional gear belts, the teethaccording to the invention have a larger on-center spacing "a" along thebelt 1'. For example, the on-center spacing "a" may be three times thelength of a conventional pitch. The on-center spacing or pitch "a" isalso larger than the width "b" of the belt 1'. Such a transport orconveyor belt may be provided on its side opposite the teeth withentraining elements or the like not shown. Even the counter elements 22may function as entraining elements for material to be transported onthe belt 1'.

The drive pinions 29, one of which is shown for example in FIG. 7, havenormally only a few recesses 35 for engagement by the teeth 23. Theon-center circumferential spacing between neighboring recesses 35corresponds to the on-center spacing "a". However, pinions having a fullnumber of teeth may also be used. In that case, the force transmissionthrough the belt 1' will be somewhat lower since not every tooth on thepinion will be engaged in a frictional force transmission. As shown inFIG. 7 the pinion 29 is secured to a shaft 30 which may be an idlingshaft or a drive shaft. The tooth pitch corresponding to the on-centerspacing "a" on the pinion 29 and on the belt 1' may be selected asdesired. However, attention must be paid to the requirement that atleast one tooth 23 must be engaging a recess 35 of the pinion 29 for anygiven looping angle of the belt 1' around the pinion 29.

FIG. 8 illustrates a link belt in which the links or teeth projectalternately from opposite sides of the belt 1", whereby two pinions 29'and 29" can be driven in synchronism, yet in opposite directions. Thepinions 29' and 29" are provided, in addition to the recesses 35, withfurther recesses 36 in which the counter elements 22 are accommodatedwhile the belt 1" passes over the respective pinion. If the counterelements 22 should not participate in the force transmission, the sizeof the recesses 36 will be slightly larger than the size of the counterelements 22.

FIG. 9a illustrates a gear belt 1a carrying teeth 26 produced asdescribed above, and intimately bonded to the counter element 22'through the webbing forming the belt 1a. The core 12 shown in FIG. 4 isso shaped that its side surfaces 28 leave a slot 28' in the tooth 26.The length of the slot 28' in the direction of the length of the tooth26, that is, in the direction of the width of the belt 1a, is shorterthan the length of the tooth 26.

The formation of a slot 28' can be avoided by beginning to withdraw thecore 12 with its side walls 28 before the completion of the injectionmolding. Thus, the core 12 would be gradually withdrawn to form a slightflat recess 28" as shown in FIG. 9b. The tooth 23' is again intimatelybonded to the counter element 22' through the belt 1b. The cross-sectionof the core 12 with its side walls 28 would be rectangular and if it isnot desired to gradually withdraw the core during the injection molding,the core can be withdrawn at the end of the injection molding, therebyleaving a rectangular opening in the tooth 23'.

Pinions for cooperation with gear belts 1a and 1b may be in the form ofsprocket wheels modified so as to have teeth of shortened height. Inother words, the tips of the teeth are removed. Such a sprocket wheelmay be provided with lateral radially outwardly extending flanges tokeep the belt trained on the sprocket wheel.

Incidentally, the teeth 23 shown in FIGS. 5 and 6 could havesemispherical configurations with circular cross-sections. Further, thecounter elements 22, 22' could have different shapes. They could, forexample, be oval or hexagonal. If desired, and depending on the intendeduse, the webbing 1 could be made of hemp fibers or of cotton or thelike.

In order to make the belts endless, their ends could be heat welded toone another where synthetic material belts are used, or conventionalconnecting clamps can be used for this purpose.

Although the invention has been described with reference to specificexample embodiments, it will be appreciated, that it is intended tocover all modifications and equivalents within the scope of the appendedclaims.

What I claim is:
 1. An injection mold for making a flexible link belthaving a flexible carrier webbing with naturally occurring holes orinterstices therein between crossing filaments and links intimatelybonded into and through said carrier webbing so that a first linkportion extends from one side of the web while a second link portionextends from the other side of the web comprising an upper mold sectionwith at least one upper mold cavity portion and a lower mold sectionalso with at least one lower mold cavity portion arranged for forming aclosed mold cavity when the mold sections are closed, means on thesections for holding said flexible carrier webbing between said upperand lower mold sections so that said flexible carrier webbing passesthrough said mold cavity, injection nozzle means extending into one ofsaid cavity portions for directly filling said one cavity portion andfor filling the other cavity portion through said holes in said flexiblecarrier webbing, and core means movably arranged and extending into theother of said cavity portions substantially opposite said injectionnozzle means for supporting said webbing against an injection moldingpressure, said core means being movable substantially perpendicularly tosaid carrier webbing.
 2. The injection mold of claim 4, wherein saidinjection nozzle means and said core means are located centrallyrelative to said mold cavity and face each other across said flexiblecarrier webbing.
 3. The injection mold of claim 2, wherein saidinjection nozzle means and said core means both contact said flexiblecarrier webbing.
 4. The injection mold of claim 2, wherein saidinjection nozzle means and said core means are closely spaced from saidflexible carrier webbing.
 5. The injection mold of claim 1, furthercomprising a tubular ejector surrounding said core means for ejecting arespective link with said webbing.
 6. The injection mold of claim 1,wherein said injection nozzle means comprise a plurality of injectionnozzles arranged in rows, said mold sections each comprising a pluralityof respective mold cavity portions for forming a plurality of moldcavities also arranged in rows for cooperation with said injectionnozzles, said means for holding being arranged for holding a pluralityof flexible carrier webbing belts in positions for passing through saidmold cavities.
 7. The injection mold of claim 1, wherein said means forholding said flexible carrier webbing comprise a projecting ring ridgein one mold section and a ring groove in the other mold section forcooperation with said ring ridge in holding said flexible carrierwebbing, said ring groove and said ring ridge surrounding the respectivecavity portion.